Method for an improved developing process in wafer photolithography

ABSTRACT

Methods and apparatus are described for improved yield and line width performance for liquid polymers and other materials. A method for minimizing precipitation of developing reactant by lowering a sudden change in pH includes: developing at least a portion of a polymer layer on a substrate with an initial charge of a developer fluid; then rinsing the polymer with an additional charge of the developer fluid so as to controllably minimize a subsequent sudden change in pH; and then rinsing the polymer with a charge of another fluid. A method for achieving a more uniform, quasi-equilibrium succession of states from the introduction of developer chemical to the wafer surface to its removal is also described. The method reduces process-induced defects and improves critical dimension (CD) control.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the field of microelectronicfabrication. More particularly, the invention relates to improving theyield and line width performance of liquid polymers.

2. Discussion of the Related Art

Lithography is one of the major drivers of semiconductor industry in itsrelentless progress in achieving smaller feature sizes with improvedyields. More specifically, improved critical dimension (CD) control andreduced process-induced defect and particle counts need to be satisfiedsimultaneously.

The “develop” fluid module process plays a significant role in thepatterning of increasingly smaller line widths. Regions of high and lowdissolution rates are created on the resist film as a result of thesequence of photolithography process steps preceding the developprocess. During a develop process, images transferred to the resistsfilm are developed into three-dimensional structures by a wet process.The subsequent etch process (mostly dry) transfers this image onto thesubstrate (Si, SiO₂, poly Si, etc.).

There are many variations of a good develop process. In general, atypical develop process has two main parts. In the first part, developerfluid is dispensed over a wafer spinning at a low rpm followed by astatic puddle formation and a long static or oscillating step at whichregions of high dissolution rate are etched away, creating 3-dimensionalimages on the film. Quality of patterned images, value of side wallangles and CD control, are all strongly affected by the first part ofthe develop process. The chemical wet etch step is immediately followedby a deionized (DI) water rinse step whose main function is to wash awaydissolved resist and developer fluid mixture with minimum particle anddefect count on the patterned wafer. Naturally, the rinse step isextremely crucial in improving yield of a lithography process.

Heretofore, the requirements of improved critical dimension control,reduced process-induced defect counts and reduced process-inducedparticle counts referred to above have not been fully met. What isneeded is a solution that simultaneously addresses all of theserequirements.

SUMMARY OF THE INVENTION

A primary goal of the invention is to improve yield. Another primarygoal of the invention is improved CD control capability. This inventionprovides a solution for both of these problems in the developer fluidmodule of a wafer track tool.

A first aspect of the invention is implemented in an embodiment that isbased on a method for minimizing precipitation of developing reactant bylowering a sudden change in pH, said method comprising: developing atleast a portion of a polymer layer on a substrate with a charge ofdeveloper fluid; then permitting at least a portion of said charge ofdeveloper fluid to dwell on said polymer so as to controllably minimizea subsequent sudden change in pH; and then rinsing said polymer with acharge of another fluid.

A second aspect of the invention is implemented in an embodiment that isbased on a method for minimizing precipitation of developing reactant bylowering a sudden change in pH, said method comprising: developing atleast a portion of a polymer layer on a substrate with an initial chargeof a developer fluid; then rinsing said polymer with an additionalcharge of said developer fluid so as to controllably minimize asubsequent sudden change in pH; and then rinsing said polymer with acharge of another fluid.

A third aspect of the invention is implemented in an embodiment that isbased on a method for minimizing precipitation of developing reactant bylowering a sudden change in pH, said method comprising: developing atleast a portion of a polymer layer on a substrate with a charge ofdeveloper fluid; then contacting said substrate with a charge of buffer,thereby mixing at least a portion of said developer fluid with at leasta portion of said charge of buffer, so as to controllably minimize asubsequent sudden change in pH; and then rinsing said polymer with acharge of another fluid.

A fourth aspect of the invention is implemented in an embodiment that isbased on an apparatus for minimizing fluid impingement force on apolymer layer to be developed on a substrate, thereby improving yieldand line width control performance, said apparatus comprising: a nozzleincluding: a manifold adapted to supply a fluid; a plurality of fluidconduits coupled to said manifold; and a plurality of tubular insertslocated within said plurality of fluid conduits.

A fifth aspect of the invention is implemented in an embodiment that isbased on an apparatus for minimizing fluid impingement force on apolymer layer to be developed on a substrate, thereby improving yieldand line width control performance, said apparatus comprising: a nozzleincluding: a developer manifold adapted to supply a developer fluid; aplurality of developer fluid orifices coupled to said developermanifold; a rinse manifold adapted to supply a rinse fluid; and aplurality of rinse fluid orifices coupled to said developer manifold,wherein said developer manifold and said rinse manifold are staggered toreduce an exterior width of said nozzle.

A sixth aspect of the invention is implemented in an embodiment that isbased on an apparatus for minimizing fluid impingement force on apolymer layer to be developed on a substrate, thereby improving yieldand line width control performance, said apparatus comprising: a nozzleincluding: a developer manifold adapted to supply a developer fluid; aplurality of developer fluid orifices coupled to said developermanifold; a rinse manifold adapted to supply a rinse fluid; a pluralityof rinse fluid orifices coupled to said rinse manifold, and saidplurality of rinse fluid orifices arranged to define at least one rinsefluid axis, wherein said nozzle is connected to a bracket adapted toraise and lower said nozzle with regard to said substrate and repositionsaid at least one rinse axis so as to be substantially coplanar with anormal to a center of said substrate.

Another aspect of the invention is to provide a method for achieving auniform, quasi-equilibrium succession of states from the introduction ofdeveloper chemical to the wafer surface, to its removal. This and otheraspects are provided in an embodiment by dispensing a substantiallyinert material onto a wafer surface prior to dispensing developer fluid,inducing a flow of developer fluid across a portion of a wafer surfacefor a time interval greater than a transit time for a fluid element toreach an outer wafer edge, the time interval prior to the substantialcompletion of the developing chemical reaction, dispensing a freshcharge of developer fluid over the wafer after a developing chemicalreaction has proceed substantially to completion, and dispensing asubstantially inert material over a wafer subsequent to dispensing thefresh charge of developer fluid.

These, and other, goals and aspects of the invention will be betterappreciated and understood when considered in conjunction with thefollowing description and the accompanying drawings. It should beunderstood, however, that the following description, while indicatingpreferred embodiments of the invention and numerous specific detailsthereof, is given by way of illustration and not of limitation. Manychanges and modifications may be made within the scope of the inventionwithout departing from the spirit thereof, and the invention includesall such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

A clear conception of the advantages and features constituting theinvention, and of the components and operation of model systems providedwith the invention, will become more readily apparent by referring tothe exemplary, and therefore nonlimiting, embodiments illustrated in thedrawings accompanying and forming a part of this specification, whereinlike reference characters (if they occur in more than one view)designate the same parts. It should be noted that the featuresillustrated in the drawings are not necessarily drawn to scale.

FIG. 1 illustrates a bottom perspective view of a multiport nozzle,representing an embodiment of the invention.

FIG. 2 illustrates a top perspective view of a multiport nozzle,representing an embodiment of the invention.

FIG. 3 illustrates a sectional view of the multiport nozzle shown inFIG. 2.

FIG. 4 illustrates a top view of a multiport nozzle, representing anembodiment of the invention.

FIG. 5 illustrates an end view of the multiport nozzle shown in FIG. 4.

FIG. 6 illustrates a sectional view of the multiport nozzle show in FIG.4 taken along section line A—A.

FIG. 7 illustrates a bottom view of the multiport nozzle shown in FIG.4.

FIG. 8 illustrates a top perspective view of the multiport nozzle shownin FIG. 4.

FIG. 9 illustrates a sectional view of the multiport nozzle shown inFIG. 4 taken along section line B—B.

FIG. 10 illustrates a sectional view of the multiport nozzle shown inFIG. 4 taken along section line C—C.

FIG. 11 illustrates a sectional view of the multiport nozzle shown inFIG. 4 taken along section line D—D.

FIG. 12A illustrates an end view of a nozzle insert, representing anembodiment of the invention.

FIG. 12B illustrates a sectional view of the nozzle insert shown in FIG.12A taken along section line F—F.

FIG. 13A illustrates an end view of a nozzle insert, representing anembodiment of the invention.

FIG. 13B illustrates a sectional view of the nozzle insert shown in FIG.13A, taken along section line E—E.

FIG. 14 illustrates a perspective sectional view of the multiport nozzleshown in FIG. 4, taken along section line A—A.

FIG. 15 illustrates develop rate as a function of the distance from thecenter of the substrate for a developer axis offset of 0 mm,representing an embodiment of the invention.

FIG. 16 illustrates develop rate as a function of the distance from thecenter of the substrate for a developer axis offset of 5 mm,representing an embodiment of the invention.

FIG. 17 illustrates develop rate as a function of the distance from thecenter of the substrate for a developer axis offset of 10 mm,representing an embodiment of the invention.

FIG. 18 illustrates develop rate as a function of the distance from thecenter of the substrate for a developer axis offset of 20 mm,representing an embodiment of the invention.

FIGS. 19A-19D illustrate develop rate as a function of spatial positionon the substrate for a developer axis offset of 0 mm, representing anembodiment of the invention.

FIGS. 20A-20D illustrate develop rate as a function of spatial positionon the substrate for a developer axis offset of 5 mm, representing anembodiment of the invention.

FIGS. 21A-21D illustrate develop rate as a function of spatial positionon the substrate for a developer axis offset of 10 mm, representing anembodiment of the invention.

FIGS. 22A-22D illustrate develop rate as a function of spatial positionon the substrate for a developer axis offset of 20 mm, representing anembodiment of the invention.

FIGS. 23A-23B are flow charts illustrating a related art develop processand a develop process according to an embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention and the various features and advantageous details thereofare explained more fully with reference to the nonlimiting embodimentsthat are illustrated in the accompanying drawings and detailed in thefollowing description of preferred embodiments. Descriptions ofwell-known components and processing techniques are omitted so as not tounnecessarily obscure the invention in detail.

The context of the invention includes photolithography processing ofmicro-structures (e.g., microelectronic structures). These structuresare typically etched and the polymers of interest function as masks toshield portions of the structures that are to remain at least largelyunaffected by the etchant. The polymers that are being developed can benegative and/or positive photoresists. The invention can also utilizedata processing methods that transform signals that characterize thestate of the polymer processing so as to actuate interconnected discretehardware elements; for example, to reposition the nozzle or change thespin rate.

The invention includes reducing defect density during the developprocess of a liquid polymer used in a photolithography step by employinga new multiport delivery apparatus (nozzle). An important aspect of themultiport delivery apparatus is reducing droplet impact. This deliverysystem resides in a developer fluid module in which a uniform laminarair flow-field preferably exists. This apparatus allows significantreduction of the defect density due to its superior rinsing action. Inaddition, this multiport nozzle system allows two different developerfluid chemistries (in addition to a rinse chemistry) to be supportedwithout any cross contamination. This delivery system for both developerfluid and deionized water reduces the impact force of the liquid(s) thuspreventing pattern collapse which is a significant yield managementproblem for small feature sizes.

The invention can be part of a developer fluid module of a wafer tracktool. In this application, the invention can be classified asinvolving 1) multiport nozzle system which supports the dispense of twodifferent developer fluid fluids without any cross-talk, 2) a secondmultiport nozzle system of same or similar geometry which is used forthe dispense of the deionized water during the rinse step, 3)implementing either parts 1) or 2) to support dual chemistry developerfluid as well as low impingement requirement throughout the developprocess. The invention includes reducing the critical dimension (CD)variation contribution of the developer fluid module by distributing thedeveloper fluid over the exposed wafer uniformly. This improves theoverall CD control capability of a wafer track system when it includessuch an apparatus in its developer fluid module. The track system can becoupled to a stepper. The term coupled, as used herein, is defined asconnected, although not necessarily directly, and not necessarilymechanically.

The invention includes helping prevent collapse of developed resiststructure or structures and it includes reducing a sudden change in pH.The term sudden, as used herein to characterize a change in pH, isdefined as a change in pH with respect to time that includes twoinflection points separated by a period of time of less thanapproximately 1 second, preferably less than approximately 0.1 second,and more preferably less than approximately 0.01 seconds. Such a nearlycongruent occurrence of two inflection points can be termed a stepfunction.

This invention includes many designs for a multi-port nozzle that can beused to deliver both developer fluid and deionized water over a polymerlayer to be developed on a substrate. The nozzle provides a geometry ofoutlets that are arranged to provide an optimal spatial liquid flow ratewhile minimizing dripping. The invention includes helping to preventcollapse of developed resist structure or structures by reducing impactforce of the liquid on the film. The invention includes providing amultiport nozzle with a nozzle insert in at least one of the ports. Theinserts can be made of a material that has a low coefficient of friction(either static or dynamic) with respect to the working fluid of thenozzle.

The invention includes extending the inserts beyond the material inwhich they are located. This extension can be internal, whereby theinserts extend into the input manifold. The extensions can be external,whereby the inserts extend beyond the bottom of the body of the nozzle.

An advantage of extending the inserts is to permit the internal manifoldto function as an air equalized reservoir, thereby affecting anequalization of static pressure with respect to the ports. An advantageof extending the inserts externally is to prevent accumulation ofresidual working fluid on the bottom surface of the body of the nozzle,notwithstanding any operational attempts to mitigate such residualaccumulation by reversing the working fluid pressure to achievesuck-back.

The invention includes staggering the working fluid manifolds. Bystaggering the working fluid manifolds, the principle axes of themanifolds can be brought closer together than would otherwise bepermitted by a non-staggered, non-intersecting configuration of theinner section of radial bores. An advantage of staggering the manifoldsis that the overall width of the multiport nozzle becomes narrower.Staggering the manifolds is useful even if there are only two manifolds,especially where the volume defined by the extent of the manifold isincreased due to the functional requirements of static pressureequalization among the ports.

The invention includes a single nozzle head that dispenses two developfluids having distinct chemistries, and one rinsing deionized water (DI)chemistry through rows of holes that are strategically placed so thatall dispensing can be done with one head position. This allows use of arotary cylinder actuator for head motion from a drain location to asingle dispense location. No servo positioning control is required. TheDI row of holes is centered for rinse of the entire wafer. The developerchemistry rows are preferably placed 5 mm offset because process datadiscussed below in more detail indicates that a 5 mm develop chemistryoffset actually improves process results. The dispense holes can havepressed in tubes with small radius ends. There are at least twoqualities of these tubes that provide benefits. First, small radius endsprovide no surface that would allow liquid to cling. Any liquid clingingat this bottom surface can cause dispensing streams to be pulled offcenter. Also, liquid on the bottom, horizontal surface can cause twostreams to join into one larger stream. This is especially problematicwhen it is critical that there is no contamination between the differentchemistries on the head. Second, forming the tips to be radial edges orends, as with pressed in tubes, allows a very smooth inner surface andeliminates aberrations that cause fluid clinging. Miniscule surfaceaberrations can cause streams to be misdirected. Rough surfaces causeuncontrolled liquid clinging which can lead to chemistry drying andcontamination. The chance of sucking back a bubble is decreased sinceliquid-air interface shape is well controlled. The “plenum” borepositions are staggered to allow 5 mm offset of developer to bemaintained and allow three chemistry rows on a 1.5″ wide head. All holesare strategically placed so that the dispense head is one piece.

FIG. 1 illustrates an embodiment of a multipart nozzle 100 fordispensing a single chemistry fluid. The nozzle 100 may have a maximumwidth measured from a front face 105 to a back face equal to the radiusof the wafer receiving the fluid. The nozzle 100 includes a main arm 110having a plurality of conduits aligned along a vertical axis withrespect to a bottom face 115 of the nozzle 100. An inlet manifold 130receives an intake fluid, and the fluid is then distributed through thenozzle and onto a rotating wafer via a plurality of outlets 101. In thisembodiment, the outlets 101 are shown to align linearly across the widthof the main arm 110. The width of the nozzle 100 allows the dispensedfluid to cover the whole wafer in one full rotation of the wafer. Assuch, the nozzle 100 provides a uniform and fast distribution of thefluid, which for developing fluid applications is a crucial requirementfor improved CD control.

FIG. 2 shows another embodiment of the present invention where amultipart nozzle 200 includes an intake manifold 230 for receivingeither one fluid or two fluids having distinct chemistries. The fluidfrom the inlet manifold may be distributed between a first arm 210 and asecond arm 220. Each arm 210, 220 may have distinct or identicalarrangement of outlets 301 (shown in FIG. 3) depending on theapplication of the nozzle 200. The nozzle 200 may also have a widthbetween a front face 205 and a back face equal to the diameter of thewafer, thereby allowing the dispensed fluid to cover the whole wafer inone full rotation of the wafer

FIG. 3 is a cross-sectional view of the nozzle 200, showing the inletmanifold 230 being divided to preferably receive two fluids havingdistinct chemistries, such as developing fluid and deionized water. Apartition 335 divides the fluid streams in the inlet manifold 230. FIG.2 shows the inlet manifold 230 guiding one fluid stream into a firstinlet channel 340. The first inlet channel 340 includes a bend 342 thatmerges with a conduit 345 in the first arm 210. The manifold guidesanother fluid stream into a second inlet channel 360. The second inletchannel 360 includes a bend 362 that merges with a second tubular insert365 in the second arm 220. Preferably, the outlets 301 on a bottom face380 of the nozzle 200 are aligned linearly across the width of thenozzle 200, although alternative arrangements are possible and will befurther described. The configuration of the nozzle 200 accommodates theuse of two different developer fluid chemistries with temperaturecontrol without any cross contamination during dispensing. The nozzle200 may be adapted to allow for deionized water dispensing, with orseparately from developing fluid dispensing. However, the nozzle 200 ofor a similar variation thereto, may also be integrated into a single ordual chemistry version of the developer fluid.

Another important feature of this invention is that the impingementforce of this nozzle is significantly reduced as compared to a singlehole nozzle due to its multi-port nature. The reduced impact force isimportant for smaller CD sizes that tend to have high aspect ratios.This makes them vulnerable to pattern collapse due to impact of thefluid. Embodiments of this invention reduce impact forces for thedeveloper fluids and the deionized water. This as such, the impingementforces throughout the develop process, may be minimized thus ensuring areliable method of patterning smaller feature sizes with higher yieldthan that provided by the know art. Another significant advantage of themultiport nozzle for use with both developer fluid and deionized wateris that it increases process latitude. In addition, the improved liquiddelivery and distribution capability of the multiport nozzle ensuresbetter overall process compliance for mechanical process variables suchas spin speed and fluid dispensing rate. Therefore, another addedadvantage provided by this invention is the potential to reduce thetotal develop process time while maintaining CD control as well as gooddefect and particle performance.

FIG. 4 illustrates another embodiment of the invention in which amultiport nozzle 400 may dispense either one or two developing fluids,and/or deionized water. Preferably, the nozzle 400 dispenses twodeveloping fluids and deionized water so that all dispensing may beaccomplished by positioning the nozzle 400 in just one position. A head420 of the nozzle 400 includes a top surface 425 having three inlets orinlet manifolds for receiving dispensing fluids and/or deionized water.In FIG. 4, one preferred arrangement provides for a first inlet 405 fora first developing fluid, a second inlet 410 for deionized water, and athird inlet 415 for a second developing fluid. Preferably, two or moreof the in lets are staggered with respect to the top surface 425 toconserve space and reduce the overall size of the nozzle 400. In FIG. 4,the first inlet 405 may be staggered from the third inlet 415, with thesecond inlet centrally located and/or offset between the first inlet 405and the third inlet 415. FIG. 5 shows an end surface 520 of the head 420with internal manifolds shown as bored chambers that correspond to theinlets. Preferably, the end surface 520 includes a first manifold 505merged with the first inlet 405 for the first developing fluid, a secondmanifold 510 merged with the second inlet 410 for deionized water, and athird manifold 515 merged with the third inlet 415 for a seconddeveloping fluid. To further reduce the dimensions of the nozzle, two ormore of the manifolds may be staggered with respect to one anotheracross the end surface. Preferably, the first manifold 510 is centrallylocated on the end face 520, with the second manifold 510 and thirdmanifold 515 symmetrically distributed on either side of the firstmanifold 505 in triangular fashion.

FIG. 6 is a cross-section cut along line A—A of FIG. 4, showing as anexample the third manifold 515 to include a plurality of conduits 670which bore vertically through the bottom surface 680 along a verticalaxis. The structure of the third manifold 515 is preferably identical tothe first and/or second manifolds 505, 510 and will be described ingreater detail as a representation of the entire embodiment. Asexemplified for the third manifold 515, each of the conduits 670 mayinclude a tubular insert 650 having an internal end 660 and an externalend 655. Preferably, the internal end 660 of each tubular insert 650extends a height internally into the third manifold 515. Fluid enteringthe third manifold 515 will not drain unless the level of the fluidcompiled within the third manifold 515 exceeds the height of theinternal end 660. As such, the internal ends 660 may define a reservoirhaving a depth defined from the internal end 660 of the tubular insert650 to a bottom manifold surface 665. In this manner, the height of theinternal end 660 may also be used to maintain the static pressure withinthe third manifold 615 constant or equal with respect to thecorresponding fluid conduit 670. Likewise, the external ends 655 of theinsert tubes 650 may extend beyond the bottom surface 680 of the nozzle400.

The tubular inserts 650 may be formed to provide a very smooth internalsurface that minimizes or eliminate surface flaws which may otherwisemisdirect a stream of developing fluids or deionized water. The smoothsurface the tubular inserts 650 also avoid the sucking back of bubbles,since the liquid-air interface within the tubular inserts 650 may becontrolled. The tubular inserts 650 also provide thin radial edges bothinside the manifolds and outside of the nozzle which reduce the area ofthe tubular inserts that may contact the fluids passing through. Thisenables the nozzle 400 to avoid problems associated with fluid streamsof developing fluids and/or deionized water that contact conduits, suchas fluid clinging or other problems that cause streams to pull ofcenter. In addition, the external ends 655 extend sufficiently beyondthe nozzle 400 to avoid streams being pulled together on the bottomsurface 680.

FIG. 7 illustrates a preferred arrangement of outlets on the bottomsurface 680 C) of the nozzle 400. The outlets may be arranged linearlyas shown, or staggered to conserve real estate. In an embodiment, acenter row 705 of outlets 701 distributes deionized water so that theentire wafer being treated may be rinsed. A second and third row 710 and715 of outlets 701 may be coupled to the second manifold 510 and thethird manifold 515 respectively to dispense at least one, and preferablytwo, developing fluids.

FIG. 8 illustrates a perspective view of the nozzle 400 incorporatingstaggered or offset inlets 405, 410, 415. The nozzle 400 may includepivotable mounting brackets 810 on a first longitudinal end 820 forsecuring the nozzle to an arm or stand above a wafer. The nozzle is alsocompact, with a preferred vertical height extending from the top surface425 to the bottom surface 680 of 1.5 inches. The nozzle 400 may includepivotable mounting brackets 810 on a first longitudinal end 820 forsecuring the nozzle to an arm or stand above a wafer. The nozzle is alsocompact, with a preferred vertical height extending from the top surface425 to the bottom surface 680 of 1.5 inches.

FIG. 9 is a cross-section of the nozzle 400 taken along lines B—B ofFIG. 4. The nozzle 400 is shown in FIG. 9 to include the first manifold505 coupled to a first plurality of tubular inserts 650 a. Likewise, thesecond manifold 510 is coupled to a second plurality of tubular inserts650 b, and the third manifold 515 is coupled to a third plurality oftubular inserts 650 c. Each of the first, second, and third tubularinserts 650 a, 650 b, 650 c preferably extend inwards into therespective first, second, and third manifold 505, 510, 515 so that theinward extensions 660 a, 660 b, 660 c of each tubular inserts define areservoir with the corresponding manifolds. The height of each reservoirwithin the manifolds 505, 510, and 515 may be individually set by thelength of the respective inward extensions 660 a, 660 b, 660 c, asdescribed in FIGS. 12 & 13 and the accompanying text.

FIG. 10 is a cross-section of the nozzle 400 taken along lines B—B ofFIG. 4. As shown by FIG. 10, each inlet may be coupled to a manifoldusing one or more chambers associated with or forming a part of themanifold. In particular, FIG. 10 shows the first inlet 405 is coupled tothe first manifold 505 with a first inlet chamber 1005, and the thirdinlet is coupled to the third manifold 515 with a third inlet chamber1015. FIG. 11 is a cross-section of the nozzle 400 taken along lines B—Bof FIG. 4. As with the other inlets and manifolds, FIG. 11 shows thesecond inlet 410 may couple to the second manifold 510 with a secondinlet chamber 1110. In other embodiments, additional inlets may coupleto corresponding manifolds using similar configurations, includingchambers. FIGS. 10 and 11 also provide another perspective of thetubular inserts 650 a, 650 b, 650 extending from the bottom surface 680of the nozzle 400 to avoid combining streams stemming from differentmanifolds.

FIGS. 12A and 12B illustrate one embodiment for a tubular inserts 650for use with this invention. As shown by FIG. 12A, the tubular insertsmay include a round cross-section 1210. However, other embodiments ofthe invention may use non-circular cross-sections, including square orpolygonal geometries. The height of the tubular insert 650 may be set byeither the vertical position of the manifold that retains the tubularinsert, or the desired depth of the reservoir defined by the internalend 660 of the tubular insert. FIG. 12A shows the tubular insert 650having a shorter height for manifolds that are closer the bottom surface680, such as the first manifold 505 or the third manifold 515.Alternatively, the tubular insert of FIG. 12A may be used to define ashallow reservoir within the second manifold 510.

FIGS. 13A and 13B illustrate another embodiment for tubular inserts. Aswith the previous embodiment, the tubular insert of FIG. 13A includes arounded cross-section. The longer length of the tubular insert shown inFIG. 13B is preferred for a manifold that is distanced from the bottomsurface 680 with respect to the other manifolds. As such, the tubularinsert 650 of FIG. 13A is preferred for the second manifold 510. Thetubular insert of FIG. 13B may also be used to create a deeper reservoirwithin the first manifold 505 or the third manifold 515. For an optimalnozzle having a depth of 1.5 inches, the tubular insert 650 may rangebetween 0.352 inches and 0.665 inches, as shown by FIGS. 12B and 13B.

FIG. 14 is a perspective cross-section of the nozzle 400. The firstinlet 405 and the second inlet 410 are shown in an off-center orstaggered arrangement on the top surface 425 of the nozzle 400. The endface 520 includes the first manifold 505 and the second manifold 510.The second manifold 510 may, for this embodiment, be viewed as exemplaryfor other manifolds in this embodiment, and will be described in greaterdetail. The second manifold 510 includes an enlarged chamber 1410. Theenlarged chamber 1410 merges with a bored segment 1420 forming theremainder of the second manifold 510. The second inlet chamber 1010couples second inlet 410 with the second manifold 510. The tubularinserts 650 b extend through the conduits 670 so that the exterior end655 extends beyond the bottom surface 680. Similarly, the interior end660 forms a height 1430 over the second manifold bottom surface 665 thatdefines a depth of the reservoir for when the second manifold 510receives fluid. In this way, fluid such as deionized water may bereceived through the second inlet 410 and expand through the boredsegment 1420 of the second manifold 510. Prior to the level of the fluidexceeding the height 1430, the fluid forms a reservoir within the secondmanifold 510. Once the fluid passes the height 1430, fluid enters thetubular insert 650 b through the interior end 660 and passes through andout of the exterior end 655. The resulting outflow of the nozzle 400may, in the case of deionized water, provide a fine disbursement ofrinsing fluid.

While not being limited to any particular performance indicator ordiagnostic identifier, preferred embodiments of the invention can beidentified one at a time by testing for the presence of a substantiallyuniform develop rate across the surface of a wafer. The test for thepresence of a substantially uniform develop rate can be carried outwithout undue experimentation by the use of the simple and conventionalIPEC Awmap rate map or spinning rate test.

A spinning rate test was performed to determine how much offset betweenthe center of a spinning wafer and the nearest develop stream could betolerated during developer dispense. The criteria used was to increaseoffset until the develop uniformity suffered. This is important to knowas such an offset is inherent in most of the dispense nozzle designsbeing considered for the develop module.

FIGS. 15-18 provide results of a develop test on wafers with nozzleoffsets of 0, 5, 10 and 20 mm at the same time while varying the spinduring dispense between 60 and 2500 rpm. The test found that an offsetat least as great as 5 mm had no adverse impact on develop uniformityacross the wafer. Presumably a nozzle design with an offset of 5 mm orless should not cause develop non-uniformity at the center of the wafer.At some point between 5 and 10 mm, fluid no longer wets the center ofthe wafer and develop there is greatly suppressed. The spin speed of thewafer interacts with the offset somewhat, and is most apparent at themarginal offset of 10 mm.

A preferred embodiment of the invention includes three parallel rows ofholes in a bar one wafer radius long. This single nozzle would dispenseboth deionized (DI) water and developer. Since the radial position ofthe arm over the wafer is done with a pneumatic cylinder, there will beonly one placement of the nozzle relative to the wafer, regardless ofwhich fluid is dispensed. Therefore, only one set of holes can beexactly over the center of the wafer, and it is expected that DIdispense should take precedence in which fluid gets to be closest to thewafer center. The typical develop process dispenses fluid on a spinningwafer, so centrifugal force will prevent fluid from reaching the centerif it is dispensed too far out. This test was performed to determine howfar off-center the develop dispense could be before develop rateuniformity across the wafer was affected.

Developer was dispensed at fixed offsets of 0, 5, 10 and 20 mm from thecenter. Initial spin during the dispense was also varied, as thedifference in centrifugal force could interact with the centering offsetto affect developer reaching the center of the wafer. Speeds of 60, 600,1200 (standard), and 2500 rpm were used.

Referring to FIGS. 19A-22D, a sub-develop technique was chosen as ameasure of develop quality for several reasons, including: (1)sub-develop technique is fast relative to line width measurements; (2)subdevelop technique has more resolution that line width or E°measurement, and is less subjective than E° measurement; (3) the entirewafer area can be used, as opposed to a few discrete locations; and (4)with exposures and develop rates well above those for E°, the effect ofthe develop process is much more dominant compared to the contributorsto develop rate, such as the swing curve, Microscan intensityuniformity, PEB uniformity, etc. As the resist film approaches completedeprotection, development trends toward a simple etch process. Inaddition to the qualitative measure of color uniformity across the waferafter development, resist removal differences across the wafer werequantified with IPEC Acumap thickness measurement system. Although thistool measures thickness at 1 mm intervals across the entire wafer(greater than 30,000 locations), as a practical matter only thethickness at the center of 121 exposure fields were used for thecalculations in this report.

The baseline chemistry, TOK9, and process were used for the test. Thedevelop recipe was modified to remove arm movement during develop and DIdispenses. A preferred embodiment of the nozzle was used for developdispense. It was adjusted so the centermost hole was over the center ofthe wafer with 0 offset in the arm program. The puddle portion of thedevelopment process was shortened from 60.5 to 5.5 seconds. The exposuredose used was 12 mJ/cm. (E° dose is approximately 6.5-7.0 mJ/cm). Thedeveloper flowmeter was set to approximately 3.8, and although volumewas not checked, past experience with this meter is that it should beabout 50 ml. All wafers were processed at one time through PEB, thenseparately into the developer, where parameters were varied for eachwafer in randomized order.

Develop rates were determined by first subtracting the resist thicknessat the 121 locations after develop from the thickness measured on two ofthe wafers after PEB, just prior to develop. In this approach, it wasassumed that wafer-wafer differences in pre-develop thickness wererelatively negligible, and a representative wafer could be the “before”wafer for all rate calculations. The resist removed was divided by thedevelop time (dispense+puddle+refresh), 10 seconds for all wafers inthis test.

Measuring initial thickness between PEB and develop is notable for tworeasons. First, many of the prior develop rate calculations have beendone using the thickness before exposure. Since the thickness loss wasabout 1000 Å from the original 8000 Å, this should be a more accurateestimate of the develop rate. Second, the exposed areas were clearlyvisible, and a characteristic pattern across the wafer was seen on everywafer. This is useful as a metric of relative deprotection across thewafer, and some papers have also noted this. It has the desirableproperty of being independent of the develop process.

The develop portion of the recipe used is as follows:

Operation Time (sec.) Speed (rpm) Arm X (mm) Spin 1.0 60-2500 0-20Develop Dispense 1.0 Same Same Develop Dispense 2.0 20 Same Spin 6.5 0Same Spin 0.5 1200 Same / / / / / / / / /

Results for this test are summarized in the table below:

St dev. Max. Min. Range Arm X Speed Ave. Rate Rate % unif % unif RateRate Rate Mm rpm Å/sec. Å/sec. (σ/ave) (mg/ave) Å/sec. Å/sec. Å/sec.Each row below corresponds to individual wafers 0 60 610.9 28.2 4.6%20.5% 679.8 554.6 125.2 0 600 639.3 2406 3.8% 16.6% 698.7 592.6 106.1 01200 608.9 21.9 3.6% 14.4% 660.7 572.8 87.9 0 1200 611.2 24.1 3.9% 17.6%677.0 569.6 107.4 0 2500 646.6 26.4 4.1% 20.6% 728.3 595.1 133.2 5 60610.0 31.1 5.1% 20.6% 685.7 560.3 125.4 5 600 622.7 28.9 4.6% 20.8%707.1 577.8 129.3 5 1200 638.8 24.4 3.8% 16.8% 698.0 590.8 107.2 5 2500647.7 23.4 3.6% 17.1% 711.9 600.8 111.1 10 60 582.6 29.2 5.0% 21.1%656.3 533.6 122.7 10 600 639.9 25.9 4.0% 20.2% 724.3 595.1 129.2 10 1200606.3 30.7 5.1% 42.0% 690.4 435.9 254.5 10 2500 639.8 32.7 5.1% 46.7%712.4 413.4 299.0 20 60 607.9 63.8 10.5% 112.9% 686.8 0.7 686.1 20 600593.8 60.0 10.1% 113.4% 672.5 −1.0 673.4 20 1200 629.4 66.6 10.6% 114.9%723.1 −0.3 723.4 20 2500 639.0 64.9 20.2% 112.0% 717.1 1.2 716.0 rowsbelow group previous data by either arm position or spin speed All 60602.8 42.4 7.0% 113.8% 686.8 0.7 686.1 All 600 623.9 42.1 6.7% 116.2%724.3 −1.0 725.2 All 1200 618.9 39.5 6.4% 116.9% 723.1 −0.3 723.4 All2500 643.3 40.4 6.3% 113.0% 728.3 1.2 727.2 0 all 623.4 29.8 4.8% 27.9%728.3 554.6 173.7 5 all 629.8 30.7 4.9% 24.1% 711.9 560.3 151.6 10 all617.2 38.3 6.2% 50.4% 724.3 413.4 310.9 20 all 617.5 66.1 10.7% 117.2%723.1 −1.0 724.1 Rows below are grouped as in previous section, but withcenter data point removed All 60 604.1 32.4 5.4% 30.1% 686.6 505.0 181.8All 600 625.1 30.8 4.9% 37.8% 724.3 487.7 236.6 All 1200 620.3 29.6 4.8%33.7% 723.1 513.9 209.2 All 2500 645.1 26.0 4.0% 33.2% 728.3 514.0 214.30 all 623.4 29.9 4.8% 27.9% 728.3 554.6 173.7 5 all 629.9 30.8 4.9%24.1% 711.9 560.3 151.6 10 all 617.9 35.9 5.8% 30.9% 724.3 533.6 190.720 all 622.7 34.6 5.6% 37.8% 723.1 487.7 235.4

Overall, the clear break in the data is between 5 and 10 mm offset. Fivemay be slightly better than 0; 20 is the worst. The primary effect isthe arm position, but the spin speed during dispense can be seen,particularly for the 10 mm offset. Predictably, the single point at thecenter is responsible for much of the non-uniformity especially for 10and 20 mm. To capture the variation between the center and the rest ofthe wafer, the range is a more useful measure of uniformity here than isstandard deviation, where the other 120 points tend to dilute thecenter.

A third order polynomial line is fitted through the data to easecomparison between the different spin speeds, as there is quite a bit ofscatter in the data FIGS. 15-18 confirm the trends seen in the tables:the primary non-uniformity is between the center and the rest of thedata for the higher speeds, 0 and 5 mm are clearly more uniform than thehigher offsets, and at 10 mm there is an interaction between offset andspeed.

FIGS. 19A-22D show the IPEC maps for all the wafers, except for onerepetition. (The maps look much better on a monitor that a printout. Themonitor also has the advantage of being able to zoom in.). The raterange spanning the different colors is held constant so that relativeuniformity can be compared between wafers. The gray and white areas areoff the scale. It can be see here, as was apparent visually on thewafers as well, that starting with 10 mm offset, a “hole” forms in thecenter where little or no develop fluid contacts the wafer, and whichhas a much lower develop rate.

The test confirmed that some offset from the center is tolerable fordeveloper dispense, at least up to 5 mm. At some point between 5 and 10mm offset from the center and the nearest develop stream, fluid ceasesto contact the center of the wafer, resulting in an area with greatlysuppressed develop rate, and no doubt catastrophic yield loss on acustomer wafer. Larger offsets exacerbate the effect. There is a mildinteraction with the spin speed used as the fluid first touches thewafer, showing up mainly at the apparently marginal condition of a 10 mmoffset. The uniformities measured were actually slightly better for the5 mm offset than for 0, but it is probably not a significant differencein this test.

These results indicate that said nozzle design should not cause developrate non-uniformities at the center of the wafer so long as thecentermost stream is not more than 5 mm from the center.

Advantages of the Invention

A process and/or nozzle, representing an embodiment of the invention,can be cost effective and advantageous for at least the followingreasons. This invention improves the CD control capability of thedeveloper fluid module. This invention reduces defects and particlesduring the develop process thereby improving the yield of the finaldevices. This invention combines low impingement force nozzle for bothdevelop and rinse parts of the process and minimizes the impinging forceon the features which are being developed, which in turn, minimizes thepattern collapsing, thus improving device yields. This invention haswide process latitude and reduced sensitivity to process variables. Thisinvention includes improved rinsing action which reduces the totaldevelop process time, thus increasing the throughput. The advantages ofthe nozzle include the enablement of an all-in-one design: three rows ofholes for two developer chemistries and one row of holes for deionizedwater chemistry in a single head, if needed. The advantages of thenozzle include a compact design, for example, a nozzle width of only 1½inches for a triple head. The advantages of the nozzle include low cost.The advantages of the nozzle include a one piece body design that iseasy to manufacture. The advantages of the nozzle include tube insertswith smooth inner surfaces for improved particle performance.

As described above and as is well understood in the art, a typicaldevelop process includes a developer dispensing step where developerfluid is dispensed directly onto a wafer. Following dispensing, thedeveloper fluid dwells on the wafer for a time period during whichchemical reactions form patterns on the wafer. Subsequently, thedeveloper fluid is removed by sequential high speed spinning and rinsingwith DI water.

The quality of the developed wafer, as measured by the quality of thepatterned images, in values of side wall angles, CD size, and otherfigures-of-merit of wafer topology (such as particle defect density), isstrongly affected by both mechanical and chemical factors involved inprocess steps. For example, during a dispensing process step, themomentum imparted by a stream of developer fluid to a micro-structure onthe wafer may be sufficient to physically damage the micro-structure.Also, as a free-surface liquid spreads over a wafer, micro-bubbles areobserved to form near a liquid-gas interfacial front travelling over thewafer surface. Such micro-bubbles adversely affect the quality of apatterned image and create particle defects. Further, chemical “shocks”may detract from the quality of a patterned image when a time scale forchemistry is so small relative to transport time scales that attendantlocal changes due to the chemical reactions can not be dissipatedrapidly enough to prevent harm to a wafer micro-structure. What ispreferred, instead, is a uniform, quasi-equilibrium succession of statesfrom the introduction of developer chemical to the wafer surface, to itsremoval.

In an embodiment, the apparatus described above is operated to cover thewafer, prior to a developer-dispensing step, with a layer of achemically inertmaterial through which the subsequently introduceddeveloper can diffuse or otherwise be brought to the wafer surface. Apreferred inert material is DI water. In an embodiment that provides alayer of an inert material, the momentum imparted by a stream ofdeveloper fluid to a micro-structure on the wafer is reduced relative toan impact against a dry wafer, lessening the probability of physicaldamage to the micro-structure and the creation of micro-bubbles.Further, when the developer is subsequently dispensed onto an inertlayer, the mechanism of diffusion acts to reduce non-uniformity over thewafer as well as to change the relative ratio of a chemical time scaleto a transport (diffusion) time scale. With developer having to diffuseto the wafer surface, the surface reaction rate may be altered ascompared to an embodiment where the developer fluid is dispenseddirectly onto the wafer surface. In a particular embodiment, the surfacereaction rate may be shifted from being controlled by chemical kinetics(rate constants) to being controlled by transport (flux due to diffusionof developer toward the wafer surface).

In an alternative embodiment, the developer process flow includes ahigh-speed spinning step substantially concurrent with developerdispensing. The spinning is at an angular speed that is sufficient toquickly induce a flow of developer toward the outer edge of the wafer.By flowing developer toward the outer edge of the wafer for a period oftime prior to the completion of the chemical reaction of the developprocess as a whole, micro-bubbles are flushed away from the surface bythe primary flow as well as secondary flows. The secondary flows areinduced in cavities that are formed by the micro-structures and aredriven by the primary flow over the micro-structures.

In a typical develop process, the chemical reaction step involving thedeveloper fluid is followed by steps in which dissolved resist anddeveloper fluid mixture are removed by spinning and DI water flushingsteps. Most preferably, this is accomplished with minimum micro-particleand defect count on the patterned wafer. During such removal steps,chemical pH temporal or spatial non-uniformity may occur, caused forexample by sudden introduction of DI water. These shocks may degrade thequality of the wafer pattern. A smoother temporal transition from the pHof developer to the pH of DI water is provided by embodiments of theinvention.

Maintaining a uniform and slowly varying chemical environment(especially with respect to pH) in comparison to abrupt removal andrinsing with DI water, an embodiment of the invention dispenses a freshcharge of developer solution onto the wafer after a dwell timeassociated with a puddle step. The developer reaction has substantiallygone to completion during the puddle step before the introduction of afresh charge. In a preferred embodiment, DI water is subsequently addedto the newly dispensed charge of developer prior to a spin-removal step.

FIGS. 23A-B illustrate a sequence of steps in a developer process of anembodiment as compared to related art. FIG. 23A illustrates a relatedart method. In FIG. 23A, develop step 2300 is shown as includingsub-steps 2310-2360. In step 2310, the wafer is rotated, followed bydispensing of developer fluid at block 2320. The developer fluid isallowed to puddle on the wafer for a dwell time at block 2330. After thechemical reactions have substantially proceeded to completion, the waferis spun at high speed at block 2340 to induce a flow of fluid toward thewafer outer edge and off of the wafer. Rinsing with DI water follows atblock 2350. Finally, the wafer is rotated to spin-dry.

In FIG. 23B, develop step 2300 is shown according to an embodiment. Thisembodiment includes including sub-steps 2315, 2325, 2332, and 2337 ascompared to FIG. 23A. At block 2315, prior to dispensing developer fluidat block 2320, an inert material such as DI water is dispensed onto thewafer. During at least a portion of the developer dispensing, the waferis rotated to induce a flow of developer fluid toward the outer edge ofthe wafer. After the developer solution has been allowed to dwell on thewafer, a fresh charge of developer is added at block 2332 followed byaddition of DI water to the newly dispensed developer at block 2337.Subsequently, the wafer may be rotated at high speed and rinsed withadditional DI water as shown in FIG. 23A.

All the disclosed embodiments of the invention described herein can berealized and practiced without undue experimentation. Although the bestmode of carrying out the invention contemplated by the inventors isdisclosed above, practice of the invention is not limited thereto.Accordingly, it will be appreciated by those skilled in the art that theinvention may be practiced otherwise than as specifically describedherein.

For example, the individual components need not be formed in thedisclosed shapes, or assembled in the disclosed configuration, but couldbe provided in virtually any shape, and assembled in virtually anyconfiguration. Further, the individual components need not be fabricatedfrom the disclosed materials, but could be fabricated from virtually anysuitable materials. Further, although the multiport nozzle describedherein can be a physically separate module, it will be manifest that themultiport nozzle may be integrated into the apparatus with which it isassociated. Furthermore, all the disclosed elements and features of eachdisclosed embodiment can be combined with, or substituted for, thedisclosed elements and features of every other disclosed embodimentexcept where such elements or features are mutually exclusive.

It will be manifest that various additions, modifications andrearrangements of the features of the invention may be made withoutdeviating from the spirit and scope of the underlying inventive concept.It is intended that the scope of the invention as defined by theappended claims and their equivalents cover all such additions,modifications, and rearrangements. The appended claims are not to beinterpreted as including means-plus-function limitations, unless such alimitation is explicitly recited in a given claim using the phrase“means-for.” Expedient embodiments of the invention are differentiatedby the appended subclaims.

What is claimed is:
 1. A method comprising: dispensing a first quantityof a substantially inert material onto a wafer surface to form a layerof substantially inert material; dispensing a first charge of developerfluid onto the surface of the wafer, such that a momentum imparted bythe first charge of developer fluid to a micro-structure on the wafersurface is reduced by the layer of substantially inert material;allowing at least a portion of developer fluid of the first charge ofdeveloper fluid to puddle on the wafer surface for a predetermined dwelltime to permit substantial completion of a developing chemical reactionto occur, a non-uniformity of the developing chemical reaction reducedby a diffusion of the puddling developer fluid through the inertmaterial; dispensing a second charge of developer fluid onto the surfaceof the wafer; and dispensing second quantity of substantially inertmaterial onto the wafer surface.
 2. The method of claim 1 furthercomprising the step of: dispensing a quantity of substantially inertmaterial onto the wafer surface subsequent to dispensing the secondcharge of developer fluid while rotating the wafer surface.
 3. Themethod of claim 2 further comprising the step of: spinning the wafersurface to achieve a selected level of dryness.
 4. The method of claim 1wherein the substantially inert material comprises deionized water. 5.The method of claim 1 wherein the developing chemical reaction iscontrolled by a flux resulting from the diffusion of the developingfluid through the inert material toward the surface of the wafer.
 6. Themethod of claim 1 wherein a variation of a pH of the developer fluidcompared to a pH of the substantially inert material is reducedthroughout a duration of the developing chemical reaction.
 7. The methodof claim 6 wherein the reduced variation of the pH of the developerfluid compared to the pH of the substantially inert material results ina reduction of developer reactants precipitating on the surface of thewafer.